1. Field of the Invention
This invention relates to a bipolar electrode which comprises an anode plate and a cathode plate separated from each other by a partition wall and electrically and structurally connected to each other, and which is suitable for electrolyzing an aqueous solution of an alkali metal chloride, etc. for the production of alkali metal chlorates or alkali metal hydroxides and chlorine, and to a method for the production of the bipolar electrode.
2. Detailed Description of the Prior Art
A conventional bipolar electrode is disclosed in U.S. Pat. No. 3,859,197 and has the structure shown in FIG. 1. In FIG. 1, reference numeral 1 represents a composite member obtained by explosive welding of a titanium plate 4 and a mild steel plate 5. The composite member 1 is fitted in an opening of a partition wall 12 composed of a titanium sheet 2 and a mild steel sheet 3 so that it forms a part of the partition wall 12. The outer edge of the titanium plate 4 of the composite member 1 is welded to an opening in the titanium sheet 2, and the outer edge portion of the mild steel plate 5 is welded to an opening in the mild steel sheet 3.
The titanium plate 4 of the composite member 1 is welded to an anode plate 7 in which titanium is a substrate thereof through a titanium spacer 6 welded to the plate 4, and the mild steel plate 5 of the composite member 1 is welded to a cathode plate 9 by means of a spacer 8 of mild steel welded to the plate 5. Thus, the anode plate 7 and the cathode plate 9 are connected electrically and structurally by the composite member 1 to form a bipolar electrode having an anode compartment 10 and a cathode compartment 11.
In conventional bipolar electrodes of this kind, the anode plate and the cathode plate are connected to the partition wall or the composite member through spacers. Since the spacers are first welded to both surfaces of the partition wall or the composite member and then the anode plate and the cathode plate are welded to the fixed spacers, it is difficult to maintain the anode plate and the cathode plate as horizontal uniform planes. In particular, since the distances to the electrode plates differ between that portion of the partition wall at which the composite member is present and the other portion of the partition wall, a difference tends to occur in the interelectrode space between the site of the spacer on the composite member and the site of the spacer on the partition wall.
In this way, the anode plate and the cathode plate in conventional bipolar electrodes form non-uniform planes, and the distance between the opposing anode and cathode cannot be maintained uniform. Consequently, this causes the defect of a non-uniform distribution of electric current.
Another defect is that since the planes of the anode plate and of the cathode plate are non-uniform, the anode and the cathode cannot be brought sufficiently close to each other, and a large loss of voltage occurs in the electrolytic cell.
Furthermore, since the distribution of electric current is non-uniform, a uniform reaction does not take place at the anode or cathode, but the reaction occurs vigorously at particular localities to cause localized heating effects. This leads to a shortening of the life of the electrodes.